All the secrets burst open, as Matron Luckes clashes with Sister Russell for leaving the London to help a family in the slums, while Dr Culpin clashes with Bennett for giving up studying to be a doctor. Mr Dean, supposedly clean, returns to work in the Operating Theatre. In the dead of night a sweatshop catches fire, bringing in scores of injured children, and the staff struggle to avert tragedy.

Dr Culpin is powerless to help when Ethel Bennett rushes to her dying brother in a naval hospital. Star surgeon Mr Dean faces destruction through his cocaine addiction. Sister Russell breaks the strict rules of Matron Luckes when she sneaks out of the London to help a young mother.

Sister Russell discovers the secret of probationer Nellie Bowers when she catches her sneaking out to see a mysterious young man. The London admits a woman brought in wearing pauper's clothes yet with silk underwear underneath. Meanwhile, the brilliant pioneer Dr Henry Head commits to performing a dangerous experiment on himself.

The strain of being 'married to the hospital' takes its toll on Sister Ada Russell, as she nears collapse. On one of the London's Jewish wards, Nurse Goodley finds herself increasingly drawn to the charismatic radical Saul Landau - but Saul has a life-threatening illness.